This is happening to me as well... working on a site for a client and they cannot see it on their end.... very embarrassing. They could see the older version of it before we began work on their site. To the best of my knowledge, no settings were changed and same with firewall and router.

The host says nothing is wrong on our end but to check to see if their IP address is blocked or black listed. Also Try to reboot the router and check the firewall and server configuration.

Any help beyond that would be greatly appreciated. Thanks

Can you post the link to your site so I can see if I can access it?

I also encounter this problem.